Air-Conditioning System for Technical Wear

ABSTRACT

The present invention relates to a thermoelectric motor ( 3 ) in which a material is interposed between the external plate ( 12 ) of a thermoelectric module and an external heat exchanger ( 4 ), to reduce heat resistance therebetween; the present invention further relates to a thermoelectric motor ( 3 ) in which the heat-carrying fluid flows directly over the internal plate ( 13 ) of a thermoelectric module, a temperature controlled garment with an inner metal layer and a convex heat exchanger.

TECHNICAL FIELD

The present invention relates to a thermoelectric motor, comprising

a thermoelectric module comprising an external plate and an internalplate with Peltier elements interposed therebetween, which are suitablefor creating a temperature difference between said external plate andsaid internal plate when energized;

an internal heat exchanger defining a working fluid guiding path so thata working liquid can exchange heat with said internal plate;

BACKGROUND OF THE INVENTION

Air-conditioning systems for clothings are known, for example, from USpatent application 2003/0019476 or international patent application WO2004/014169.

These documents describe garments having substantially similarstructures: they contain a heat-carrying fluid, generally water, whichflows in a canalization system formed within the thickness of thegarment and feature a thermoelectric device allowing to heat or cool theheat-carrying fluid regardless of the environmental conditions.

In other words, the thermoelectric device creates a controlledmicroclimate within the garment, so that the body of the wearer is notexposed to too high or too low outer temperatures.

Thermoelectric devices are now commonly made by combined use ofthermoelectric modules and suitable heat exchangers. Thermoelectricmodules are made using semiconductor materials which exploit the Peltiereffect to heat or cool two opposed plates.

This system is particularly advantageous because it is both sturdy andreversible; this means that, by supplying electric current having acertain polarity, one plate is heated and the other is cooled; byinverting the polarity of the electric current supplied to thethermoelectric module, the opposite effect can be obtained.

Two heat exchangers are usually connected to the thermoelectric module:one for exchanging heat with the external environment (air) and anotherfor exchanging heat with the heat-carrying fluid (water).

Applications have so far always had a relatively low thermal efficiency,never enough for application on sportswear garments: a low thermalefficiency requires the supply of considerable power for operating thethermoelectric device.

Particularly, in motorcycle racing, power cannot be easily drawn fromthe motorcycle motor, as performances might be unacceptably affectedthereby: even a few hundredths of a second can make the difference in acompetition.

Therefore, a device having a standalone power source (such as abattery), which could provide the garment with enough power to cover thewhole duration of a race would allow a motorcyclist to race withoutbeing exposed to environmental hot or cold conditions; therefore, thedriver would not have to use his/her own psychophysical resources toresist environmental temperature and could concentrate on driving only.

In view of the prior art as described above, the object of the presentinvention is to provide a garment with a thermoelectric device having ahigher efficiency than in prior art, to be able to provide anair-conditioned motorcycling suit.

SUMMARY OF THE INVENTION

According to the present invention, this object is achieved by athermoelectric motor, comprising:

a thermoelectric module comprising an external plate and an internalplate with Peltier elements interposed therebetween, which are suitablefor creating a temperature difference between said external plate andsaid internal plate when energized;

an internal heat exchanger defining a working fluid guiding path so thata working liquid can exchange heat with said internal plate;

wherein said fluid path of said internal heat exchanger allows suchworking liquid to flow directly over said internal plate, at least overa contact area, so that said internal plate directly exchanges heat withsaid working liquid;said thermoelectric motor further comprising:

an external heat exchanger for exchanging heat with the externalenvironment;

a thermoelectric module comprising an external plate and an internalplate with Peltier elements interposed therebetween, which are suitableto create a temperature difference between said external plate and saidinternal plate when energized;

said external plate of said thermoelectric module being in thermalcontact with said external heat exchanger;wherein a material is interposed between said external plate and saidexternal heat exchanger, having a thermal resistance per unit area ofless than 0.05 cm²° C./W.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will appear fromthe following detailed description of one practical embodiment, which isillustrated without limitation in the annexed drawings, in which:

FIG. 1 is a schematic view of a motorcycle racer wearing a motorcyclingsuit having a so-called “hump”,

FIG. 2 is an exploded perspective view of a thermoelectric deviceaccording to a preferred embodiment of this invention,

FIG. 3 is a schematic sectional view of a garment according to apreferred embodiment of this invention,

FIG. 4 is a schematic view of a preferred embodiment of this invention,

FIG. 5 is an exploded perspective view of a micro-finned exchangerhaving two thermoelectric modules according to a preferred embodiment ofthis invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, numeral 1 designates a protective motorcycling suit; it isgenerally equipped with an additional element 2, known as “hump”, whichis designed both to prevent turbulence in the area behind the helmet andto protect the neck from excessive torsion backwards.

FIG. 2 schematically shows the thermoelectric motor 3: it is made up bya first heat exchanger 4 and by a second heat exchanger 7, both of thembeing in thermal connection with one or more thermoelectric modules 11.

The thermoelectric modules 11 are normal Peltier thermoelectric modules,which are made by semiconductor material interposed between an externalplate 12 and an internal plate 13.

An external heat exchanger 4 allows heat transfer between thethermoelectric module/s 11 and the external environment.

An internal heat exchanger 7 allows heat transfer between thethermoelectric module/s 11 and the heat-carrying fluid.

The external environment, the external heat exchanger 4 and the externalplate 12 thus form a chain of elements in series which allow heattransfer from the external plate to the external environment or viceversa.

When the heat-carrying fluid is to be cooled and heat is to be releasedto the external environment, the external plate 12 acts as a hot source;when the heat-carrying fluid has to be heated, it will act as a coldsource.

Maximum efficiency requires minimization of thermal resistances amongthe elements of the chain, and particularly those at the interfacebetween the external heat exchanger 4 and the external plate 12.

Both the external plate 12 of the thermoelectric module 11 and thebottom surface 5 of the external heat exchanger 4 are formed with adefined surface roughness, which limits actual contact between the twosurfaces to a fraction of the overall extension of the surfacesthemselves.

To avoid the need of particularly complex mechanical working, a fillingmaterial (not shown) is interposed between the bottom surface 5 of theexternal exchanger 4 and the external plate 12 of the thermoelectricmodule 11, which material can adapt its shape both to the bottom surface5 of the external exchanger 4 and to the top surface of the externalplate 13, thereby avoiding any effect caused by surface roughness.

Such filling material may have a high ductility and a high thermalconductivity, for instance it can be a metal oxide-based thermallyconductive paste, or graphite-based high conductivity thermalinterfaces, or a phase transition conductive material, i.e. having amelting point of 50° C. to 100° C.

Advantageously, the thickness of this intermediate layer is of 50 to 200micrometers.

The graphite layer is applied by interposing it between the two surfacesand exerting enough pressure thereon to deform it (e.g. a pressure of 1to 15 bar), whereas the layer of the phase-transition thermallyconductive paste is applied as follows: first, the paste is interposedbetween the two surfaces, then the temperature of the thermoelectricmodule 11 is increased above the melting point of the paste, to causeliquefaction thereof, and finally such temperature is decreased to causere-solidification; thus, the temporary liquid layer allows theintermediate layer to take the form of the two surfaces, perfectlyadapting to the roughness of the two surfaces 5 and 13.

The external heat exchanger 4 is designed to have as large heat exchangesurface as possible.

One limitation to the shape of the exchanger is that it has to beaccommodated in the hump 2 of the suit 1 of the motorcycle racer.

These humps mat have various shapes: all of them have a convex outersurface and a radius of curvature which is generally in a range of 80 to160 mm.

A first option is to form the external heat exchanger 4 with one or morefins 5 allowing heat transfer with the surrounding environment.

Therefore, the external exchanger may be formed from aluminum or analloy thereof, preferably as a monobloc, to combine the advantages oflight weight, good heat conductivity and thermal isotropy, or for astill lighter weight, from graphite or a graphite-based material.

When the external exchanger 4 is formed from graphite, it is fabricatedby superposing a plurality of sheets so that their planes are parallelto the planes of the fins 5; the graphite exchanger 4 is thereforethermally anisotropic, that is, has a very good heat conductivity(approximately equivalent to copper), along the preferred plane definedby the sheets, but substantially acts as an insulator perpendicular tosuch plane.

Advantageously, the bottom surface 5 of the external exchanger 4, whenconsidered in the direction perpendicular to the preferred heatconduction plane of graphite is substantially as large as the externalplate 13 of the thermal module 11, when considered in the samedirection.

Whenever multiple thermoelectric modules 11 are provided, they can begenerally considered as a thermoelectric unit, composed of suchplurality of thermoelectric modules 11.

The thermoelectric modules 11 may be disposed in parallel arrangementswithin s thermoelectric unit, in rows, columns or in any otherarrangement.

This may provide a graphite heat exchanger of greater width than asingle thermoelectric module 11, wherefore the outer surface of the humpmay be totally used.

The thermoelectric unit will have its own extension both along the axisperpendicular to the preferred heat conduction plane of the graphite andin the direction perpendicular thereto; the above geometricconsiderations related to single thermoelectric modules will applythereto.

Such heat exchanger 4 with fins 5 may have such construction as to beentirely contained in the outer profile of the hump or, moreadvantageously, to at least partially project therefrom.

In the latter case, the fins of the heat exchanger are at least partlyin the air flow path around the racer.

To improve heat exchange efficiency without affecting the aerodynamicsof the motorcycle/racer assembly, the suit may be formed with front airpassages, e.g. on the shoulders, which are connected to conduitscarrying the air introduced therein to the external exchanger 4.

By suitably sizing the air passages and the conduits in the suit, an airflow may be directed through the fins 5 of the external exchanger, whichflow may be sufficient to ensure proper operation of the thermal device3 with no need for marked external extensions on the suit hump.

Alternately, as shown in FIG. 5, the external exchanger 4 may beequipped with micro-finned elements, i.e. thermally conductive elements,preferably made of metal, of small thickness, generally below 30 mm andpreferably below 15 mm, whose top profile does not have real fins, butteeth and grooves, e.g. triangular, which increase the heat exchangesurface to air.

These grooves or teeth may advantageously have a pitch of 1 mm to 5 mm,and the distance between the groove bottoms and the teeth tops may be inthe same range.

This second type of external exchanger is more compact than the externalfinned exchanger and does not suffer from its aerodynamic drawbacks;therefore, it can be directly incorporated in the hump without requiringair flow conveying systems.

Advantageously, the micro-finned exchanger has a curved average outerprofile, with a radius of curvature generally from 80 mm to 160 mm, toobtain a curvature substantially corresponding to that of the hump to becovered and/or replaced thereby.

If the exchanger will have to be incorporated in the hump, it will bedisposed by exposing to the external environment its heat exchangingsurface only, so that the aerodynamic performances of the hump are notaffected.

A third alternative consists in forming the external exchanger with athermally conductive porous material.

Substantially porous materials, e.g. formed of more or less regular wirehanks, are not suitable for the purpose and cannot be considered asporous metal materials for the purposes of this disclosure.

These hanks have a small contact surface between wires and cannot ensurean adequate heat exchange.

Porous materials as mentioned herein are materials having a metal matrixwith cavities therein, such as those disclosed in patent application WO06/31306.

Heat exchangers formed from thermally conductive porous materials havethe advantage of a lighter weight, assuming an equal amount of exchangedthermal power, and are better suited for the proposed application.

The heat-carrying fluid, the internal plate 13 and the thermoelectricmodule 11 and, in case, the circulation pump, form the second chain ofelements in series for transferring heat from the internal plate to theheat-carrying fluid or vice versa.

The heat-carrying fluid may include, for instance, a mixture of waterand alcohol, Freon, or any other heat-carrying fluid commonly used inthe field of refrigeration.

Like in the previous case, the internal plate 13 may either be the hotsource, if the heat-carrying fluid has to be heated, or the cold source,if it has to be cooled.

To minimize thermal resistances at the interface between theheat-carrying fluid and the internal plate 13, the internal exchanger 7is formed so that the heat-carrying fluid flowing therethrough passesdirectly over the internal plate 13 to directly eliminate any thermalresistance therebetween.

For this purpose, the internal heat exchanger 7 has a main hollow body,with a heat-carrying fluid inlet conduit 8 and a heat-carrying fluidoutlet conduit 9 and one or more ports 10.

Therefore, the inner cavity of the internal heat exchanger 7 is at leastpartly directly delimited by the one or more internal plates 13 of theone or more thermoelectric modules 11 at the one or more ports 10.

The internal plate 13 of the thermoelectric module (or the internalplates 13 of the thermoelectric modules 11) is attached, e.g. glued, atits outer periphery, to provide a water-tight seal and prevent theheat-carrying liquid from leaking therefrom. Alternatively, it can befastened by using a seal and fastening screws.

The inner cavity advantageously comprises means (not shown) forincreasing turbulence in the heat-carrying fluid flow, such asprotuberances arranged in a regular or irregular pattern, andadvantageously formed on the surface of the inner cavity which isopposite the part formed by the internal plate 13 of the thermoelectricmodule 11.

For size-reducing purposes, the circulation pump may be advantageouslyincorporated in the internal heat exchanger.

The heat-carrying fluid flowing out of the conduit 9 of the internalexchanger 7 is introduced in a garment, e.g. covering the racer's trunk,such as a suit, a vest or a jacket, for heat exchange with the body ofthe racer.

Once again, the efficiency of the heat exchanger has to be optimized byreducing thermal resistances; FIG. 3 schematically shows an embodimentof this invention which provides this additional advantage.

The garment of this invention comprises an inner metal layer 14, whichmay be in contact with the racer's body, preferably formed of a metalmesh.

Such inner metal layer 14 has a network of conduits attached thereto,through which the heat-carrying fluid flows.

The conduits 15 are preferably welded to the inner metal layer 14.

For the conduits 15 to be welded to the inner metal layer 14, the latteris covered by a layer 16 of a polymer material, preferably polyurethane,to allow a structure 17, preferably made from the same polymer as thelayer 16, to be later welded thereto.

A support 19 is provided in the conduits 15, which prevents thestructure 17 from collapsing onto the layer 16; such collapse wouldcause the conduit 15 to be throttled and occluded, which would preventeffective operation of the air-conditioning system.

Currently available motorcycling suits may be essentially divided intotwo types: a first type with a central hinge, and a second type with twohinges, arranged symmetrically at the trunk sides, which hold aseparable central element.

To achieve the advantages this invention from this second suit type, twoinner wings are provided, which extend from the suit sizes under thehinges and towards the center of the trunk, and cover the area incontact with the racer's trunk during use.

In this case, the conduits 15 are formed within the wings which may bein turn advantageously equipped with devices (such as a central hinge)to hold the central edges close together.

As schematically shown in FIG. 4, the garments manufactured according tothis invention may advantageously comprise a control and monitoringsystem 20, having one or more humidity 21 and/or temperature sensors 22.

The control and monitoring system 20 receives signals from one or moresensors 21, 22 and, based on such signals, it determines the optimaloperating conditions for the thermoelectric motor 3.

Therefore, the air-conditioning system can use the feedback provided bythe humidity and/or temperature values detected from the racer's body;operation may be also designed to be a fixed-temperature operationand/or based on external temperature.

According to a further preferred embodiment, the air-conditioned garmentmay advantageously comprise batteries, preferably lithium batteries,connected to thermoelectric motor 3 and to control and monitoring system20, for supplying power to them; it can also have means for connectingto a remote power source, such as a cable for connecting to the mainsand allow both recharging and normal operation thereof.

Thus battery life may be used only when required, e.g. during the raceor tests, at the same time keeping the advantages of theair-conditioning throughout the race preparation time, in which themotorcycle is still at boxes, without reducing the battery life.

In practice, a number of specific embodiments may be envisaged,according to the following examples:

Example A

A thermoelectric motor 3 comprising:

a thermoelectric module 11 comprising an external plate and an internalplate 13 with Peltier elements interposed therebetween, which aresuitable for creatin a temperature difference between said externalplate 12 and said internal plate 13 when energized;

an internal heat exchanger 7 defining a working fluid guiding path sothat said fluid can exchange heat with said internal plate 13;

wherein said fluid path of said internal heat exchanger 7 allows suchheat-carrying fluid to flow directly over said internal plate 13, atleast over a contact area, so that said internal plate 13 directlyexchanges heat with said heat-carrying fluid.

Example B

A thermoelectric motor 3 according to example A, wherein said internalheat exchanger 7 has protuberances for increasing the turbulence of saidheat-carrying fluid flow at said contact area.

Example C

A thermoelectric motor 3 according to examples A or B, wherein saidinternal heat exchanger 7 further has inlet 8 and outlet 9 ports for theheat-carrying fluid and at least one opening 10 at said contact area,said opening 10 being closed by said internal plate 13.

Example D

A thermoelectric motor 3 according to example C, wherein said internalplate 13 is glued to said internal heat exchanger 7.

Example E

A thermoelectric motor 3, comprising:

an external heat exchanger 4 for exchanging heat with the externalenvironment;

a thermoelectric module 11 comprising an external plate and an internalplate 13 with Peltier elements interposed therebetween, which aresuitable to create a temperature difference between said external plate12 and said internal plate 13 when energized;

said external plate 12 of said thermoelectric module 11 being in thermalcontact with said external heat exchanger 4;wherein a material is interposed between said external plate 12 and saidexternal heat exchanger 4, having a thermal resistance per unit area ofless than 0.05 cm²° C./W.

Example F

A thermoelectric motor 3 according to the example E, wherein saidmaterial is selected from the group consisting of: graphite,graphite-containing materials, phase transition thermal pastes.

Example G

A thermoelectric motor 3 according to the example F, wherein said phasetransition thermal paste has a melting point above 50° C. and below 100°C.

Example H

A thermoelectric motor 3 according to the examples E, F or G, whereinsaid external heat exchanger 4 is made from a material selected from thegroup consisting of: aluminum, aluminum alloys, graphite, materialswhich substantially comprise graphite.

Example I

A thermoelectric motor 3 according to the examples E, F, G or G, whereinsaid external heat exchanger 4 has one or more heat exchanging fins 5for exchanging heat with ambient air.

Example J

A thermoelectric motor 3 according to the example I, wherein saidexternal heat exchanger 4 is formed of graphite sheets in sucharrangement that the main planes of said fins 5 are parallel to saidgraphite sheets.

Example K

A thermoelectric motor 3 according to the example J, wherein saidexternal heat exchanger 4 has a size, as measured perpendicular to saidpreferred heat conduction plane, which is substantially not larger thanthe overall size, as measured along the same axis, of saidthermoelectric module 11.

Example L

A thermoelectric motor 3 according to the example J, comprising aplurality of said thermoelectric modules 11, together forming athermoelectric unit, wherein said external heat exchanger 4 has a size,as measured perpendicular to said preferred heat conduction plane, whichis substantially not larger than the overall size, as measured along thesame axis, of said thermoelectric module 11.

Example M

A thermoelectric motor 3 according to the examples E, F, G or H, whereinsaid external heat exchanger 4 is microporous or microfinned.

Example N

An air-conditioned garment comprising a thermoelectric motor 3 accordingto the examples A, B, C or D, and/or according to the examples E to M.

Example N

An air-conditioned garment according to the example M, wherein saidgarment is a motorcycling suit 1 having a hump 2 on the upper part ofthe back of the suit, said thermoelectric motor 3 being provided at saidhump 2.

Example O

An air-conditioned garment according to the example M, wherein saidexternal heat exchanger 4 is according to the examples I, J or K, andsaid garment has one or more air passages, preferably formed at theshoulders, and comprises one or more conduits for putting said one ormore air passages in fluid communication with the external heatexchanger 4 of said thermoelectric motor 3, so that, when air flows inthrough said air passages, it can be guided to provide heat exchangewith said external exchanger 4.

Example P

An air-conditioned garment according to the example N, wherein saidexternal heat exchanger 4 is according to the example 12 and is locatedin the proximity of the outer surface of said hump 3 so that the airflow generated around said garment can flow thereon.

Example Q

An air-conditioned garment according to the examples N, O or P, furthercomprising one or more humidity sensors 21 and preferably also one ormore temperature sensors 22, said humidity sensors 21 being adapted tosense the humidity in the internal spaces of the garment, generated bythe wearer's perspiration.

Example R

An air-conditioned garment according to the example Q, comprising adevice 20 for receiving signals form said sensors 21, 22 and controllingthe operation of said thermoelectric motor 3 based on said receivedsignals.

Example S

An air-conditioned garment according to the examples N, O, P, Q or R,comprising one or more batteries suitable for powering saidthermoelectric module.

Example T

An air-conditioned garment according to the examples N, O, P, Q, R or S,comprising means for connection to an external power source, forenergizing said thermoelectric module from said external power source.

Example U

An air-conditioned garment comprising an inner metal layer 14, whereinsaid inner metal layer 14 lies on at least a portion of the surface ofsaid garment that, with the garment being worn by a wearer, facestowards the body of said wearer.

Example V

An air-conditioned garment according to the example U, wherein saidmetal layer 14 is a metal mesh.

Example W

An air-conditioned garment according to the examples U or V, whereinsaid metal layer 14 is covered by a polymer, for instance of thepolyurethane type.

Example X

An air-conditioned garment according to the example X, comprising anetwork of conduits 15 which is welded to said polymer that covers saidmetal layer 14, said network of conduits 15 being for instance formedfrom the same polymer as the one that covers said metal layer 14.

Example Y

An air-conditioned garment according to the example X, comprising arigid support 19, substantially adapted to prevent occlusion of theconduits of said network of conduits 15 during normal use of saidair-conditioned garment, said support 19 being for instance formed fromthe same material as said network of conduits 15.

Example Z

A heat exchanger 4 of micro-finned or microporous material, having aconvex main heat exchanging surface having an average radius ofcurvature of 80 to 160 mm, for instance being configured to allowassociation thereof to the hump of a motorcycling suit, so that thecontour of said hump associated to said heat exchanger is not more than5 mm from the contour of said hump before application of said exchanger.

Those skilled in the art will obviously appreciate that a number ofchanges and variants may be made to the arrangements as describedhereinbefore to meet incidental and specific needs, without departingfrom the scope of the invention, as defined in the following claims.

1. Thermoelectric motor, comprising: a thermoelectric module comprisingan external plate and an internal plate with Peltier elements interposedtherebetween, which are suitable for creating a temperature differencebetween said external plate and said internal plate when energized; aninternal heat exchanger defining a working fluid guiding path so that aworking liquid can exchange heat with said internal plate; wherein saidfluid path of said internal heat exchanger allows such working liquid toflow directly over said internal plate, at least over a contact area, sothat said internal plate directly exchanges heat with said workingliquid; said thermoelectric motor further comprising: an external heatexchanger for exchanging heat with the external environment; athermoelectric module comprising an external plate and an internal platewith Peltier elements interposed therebetween, which are suitable tocreate a temperature difference between said external plate and saidinternal plate when energized; said external plate of saidthermoelectric module being in thermal contact with said external heatexchanger; wherein a material is interposed between said external plateand said external heat exchanger, having a thermal resistance per unitarea of less than 0.05 cm²° C./W.
 2. A thermoelectric motor as claimedin any one of claim 1, wherein said internal heat exchanger further hasinlet and outlet ports for the heat-carrying fluid and at least oneopening at said contact area, said opening being closed by said internalplate.
 3. A thermoelectric motor as claimed in claim 2, wherein saidinternal heat exchanger has protuberances for increasing the turbulenceof said heat-carrying fluid flow at said contact area.
 4. Athermoelectric motor as claimed in claim 3, wherein said internal plateis glued to said internal heat exchanger.
 5. A thermoelectric motor asclaimed in claim 1, wherein said material is selected from the groupconsisting of: graphite, graphite-containing materials, phase transitionthermal pastes.
 6. A thermoelectric motor as claimed in claim 5, whereinsaid phase transition thermal paste has a melting point above 50° C. andbelow 100° C.
 7. A thermoelectric motor as claimed in claim 2, whereinsaid external heat exchanger is made from a material selected from thegroup consisting of: aluminum, aluminum alloys, graphite, materialswhich substantially comprise graphite.
 8. A thermoelectric motor asclaimed in claim 7, wherein said external heat exchanger has one or moreheat exchanging fins for exchanging heat with ambient air.
 9. Athermoelectric motor as claimed in claim 8, wherein said external heatexchanger is formed of graphite sheets in such arrangement that the mainplanes of said fins are parallel to said graphite sheets.
 10. Athermoelectric motor as claimed in claim 9, wherein said external heatexchanger has a size, as measured perpendicular to said preferred heatconduction plane, which is substantially not larger than the overallsize, as measured along the same axis, of said thermoelectric module.11. A thermoelectric motor as claimed in claim 9, comprising a pluralityof said thermoelectric modules, together forming a thermoelectric unit,wherein said external heat exchanger has a size, as measuredperpendicular to said preferred heat conduction plane, which issubstantially not larger than the overall size, as measured along thesame axis, of said thermoelectric module.